GB2079190A

GB2079190A - Particle Separating Apparatus

Info

Publication number: GB2079190A
Application number: GB8022154A
Authority: GB
Original assignee: Ishikawajima Harima Heavy Industries Co Ltd
Current assignee: IHI Corp
Priority date: 1980-07-07
Filing date: 1980-07-07
Publication date: 1982-01-20
Also published as: GB2079190B

Abstract

A particle separating apparatus has a lower portion 1 connected to an intermediate portion 2 which in turn is connected to an upper portion 3. The lower portion is in the form of a downwardly convergent conical hopper having an outlet 4 for separated particles. The intermediate portion is substantially cylindrical and has a gas inlet 5 positioned so that the incoming gas is caused to revolve or spiral within the intermediate portion. The upper portion has a top wall 7 spaced from the gas inlet 5 through which a coaxial gas discharge pipe 6 extends. Two diametrically opposed outwardly extending material trapping chambers 8 are positioned adjacent the top wall 7 communicating with the interior of the upper portion and trap those particles which are carried upwardly by the gas spiralling upwards from the inlet 5 to the discharge 6. A number of such an apparatus may be connected in series and serve as heaters in which cement or alumina raw materials are preheated by exhaust gases discharged from a rotary kiln. <IMAGE>

Description

SPECIFICATION Particle Separating Apparatus The present invention relates to apparatus for separating particles from a particle-laden gas and is particularly concerned with such apparatus for removing dust from a dust-laden gas, especially for use in a process for calcining cement or alumina particles.

Figure 1 shows a dust separator which has been used in cement calcination comprising a cyclone for separating and heating particles of raw materials and which has a high separation efficiency and a simple construction. In operation, a high temperature gas laden with particles flows through an inlet duct b tangentially into the cylindrical portion a of the cyclone at an inlet velocity of from 10 to 20 metres per second. The cyclindrical portion has a top wall c through which extends a gas outlet pipe d, and the gas is forced to spiral downward along the cylindrical wall e and the downwardly convergent conical wall f while the particles, by virtue of their mass, are flung outwardly against these walls. Thereafter, the gas spirals upward within the downwardly spiralling gas vortex and flows into the gas outlet pipe d.

However, the cyclone a inherently has a high pressure loss. In a single stage apparatus, the pressure loss ranges from 100 to 1 50 mmAq and in the case of a four stage apparatus, the pressure loss ranges from 400 to 600 mmAq. As a result, the power consumption of blowers and exhaust fans increases. The pressure loss across the cyclone a is mainly due to the energy loss due to the forced formation of the two vortices. In general, the pressure loss is proportional to the square of the inlet velocity of the gas. It follows, therefore, that when the inlet velocity or head is substantially reduced to the order of less than 10 metres per second, the pressure loss can be considerably decreased, but the cyclone must be increased in size accordingly. Therefore this known apparatus is unsatisfactory in practice.

According to the present invention there is provided a particle separating apparatus having a lower portion, an intermediate portion and an upper portion in which the lower portion is in the form of a conical hopper having at its lower end an outlet for separated particles, the intermediate portion is substantially cylindrical and has a gas inlet pipe so positioned that, in use, the incoming particle laden gas is caused to revolve or spiral within the intermediate body and the upper portion has a top wall spaced from the gas inlet through which a gas discharge pipe extends whereby, in use, the incoming gas spirals upwards and the particles are separated from it and collected.

The preferred embodiment includes at least one upper trapping chamber communicating with the interior or the upper portion through a respective opening in the wall of the upper portion, whereby, in use, those particles which are carried upwardly with the gas pass into the trapping chamber and are collected.

Conveniently there are two substantially diametrically opposed upper trapping chambers extending substantially tangentially outwardly from the upper portion.

The invention also embraces a material treatment apparatus, such as a cement calcination apparatus, including a furnace or kiln and a raw material particle preheater including such a particle separating apparatus through which, in use, hot gas from the furnace or kiln flows and the raw material particles are preheated.

Further features and details of the present invention will be apparent from the following description of one preferred embodiment which is given by way of example with reference to Figures 2 to 7 of the accompanying drawings in which: Figure 2 is a schematic sectional eievation of the preferred embodiment of the present invention; Figure 3 is a cross sectional view taken along the line Ill-Ill in Figure 2; Figure 4 is a cross sectional view taken along the line IV--IV in Figure 2; Figure 5 is a block diagram of a cement calcination apparatus incorporating particle separators in accordance with the present invention; and Figure 6 and 7 are further diagrams similar to Figure 5 of different cement calcination apparatus incorporating particle separators in accordance with the present invention.

Referring firstly to Figures 2 to 4 a cyclone in accordance with the present invention, which may be used as a raw material particle preheater, has a lower body 1, an intermediate body 2 and an upper body 3. The lower body 1 is in the form of a downwardly convergent conical hopper forming a lower trapping chamber and having its outlet connected to a particle discharge chute 4 via a valve 9. The intermediate body 2, which is joined to the upper end of the lower body 1, is in the form of a cylinder, and an inlet duct 5 is connected to the intermediate body 2 tangentially or so as to form a volute so that the incoming particle-laden gas is forced to rotate within the intermediate body 2. The upper body 3, which is joined to the upper end of the intermediate body 2, is substantially frustoconical and has an upper wall 7.The distance between the upper edge of the inlet 5 and the top wall 7 of the upper body 3 is preferably greater than a quarter, or a half, of the internal diameter of the intermediate cylinder 2 and in this embodiment is in fact greater than this diameter. A gas outlet pipe 6 extends coaxially through the top wall 7. Whilst the cross section of the upper body 3 is circular, the upper body 3 may alternatively be a cylinder or a combination of a cylinder and a frustum. At the upper end of the upper body 3 there are two substantially diametrically opposed upper particle trapping chambers 8 extending tangentially outwardly from the body 3 contiguous with the top wall 7 and communicating with the interior of the upper body 3 through openings formed through its side wall.Those particles which are carried upwardly are trapped in the particle trapping chambers 8 and then discharged through particle discharge chutes 10, each of which includes a valve 11. The particles are charged into the inlet duct 5 through a particle supply chute 12 including a valve 13. The solid arrows G indicate the flow of the gas while the dotted arrows M indicate the raw material particles.

The mode of operation of the particle separator is as follows. When the particle-laden gas flows through the inlet 5 into the intermediate body 2, it revolves or spirals, as shown in Figures 2 and 4.

Part of the gas carrying the particles spirals upwards along the inner wall surface of the upper body 3, forming a free vortex so that the particles are flung against the inner wall of the upper body 3 by virtue of their inertia and the centrifugal forces acting on them. The gas free from the particles flows into the gas outlet pipe 6, and the majority of the particles drop down the wall into the lower body 1 and are discharged through the discharge chute 4.

Those particles which remain entrained in the upwardly spiralling gas are flung outwards into the trapping chambers 8 under the action of the centrifugal force imparted to them by their swirling motion and are trapped there. The particles trapped in the particle trapping chambers 8 are discharged through the particle discharge chutes 10 into the discharge chute 4.

Some applications of the particle separator described above will now be described in conjunction with the cement calcination process.

In the apparatus illustrated in Figure 5, five particle separators A, B, C, D and E in series are used as suspension heaters in which the cement raw materials are preheated by the exhaust gases discharged from a rotary kiln 14. The number of suspension preheaters can be increased or decreased in accordance with requirements.

The high temperature exhaust gases discharged from the rotary kiln 14 flow through the suspension preheaters in the order E, D, C, B and A and are discharged from the uppermost preheater A by an exhaust fan 18. The raw material particles are first charged into the air duct connecting the preheaters A and B. The particles trapped in the upper and lower trapping chambers of the preheater A are charged into an air duct connecting the preheaters B and C. The remaining preheaters are connected in a similar manner, and after passing through all the preheaters the particles are finally charged into the rotary kiln 14 from the lowermost preheater E.

The particles are calcined and the clinker is cooled in a clinker cooler 1 5.

In the apparatus illustrated in Figure 6, the particle separators A to E are used as so-called "new suspension preheaters" in which a calcining furnace 1 6 with a burner 1 7 is interposed between the rotary kiln and the lowermost preheater E. The mode of operation of the apparatus is substantially similar to that of the apparatus shown in Figure 5 except that part of the preheated air from the cooler 1 5, the exhaust gases from the rotary kiln 14, part of the fuel supplied from the burner 1 7 and the preheated raw materials from the fourth stage D are introduced into the furnace 1 6 and then into the last stage E from which the exhaust gases are charged into the fourth stage D while the preheated raw materials are charged into the rotary kiln 14.

In the apparatus shown in Figure 7, the furnace 1 6 is omitted and instead the burner 17 is attached to the last preheater stage E to burn the fuel. Therefore the last stage E functions not only as a particle separator but also as a calcining furnace It will be understood that in the apparatus shown in Figures 5, 6 and 7, one or more of the particle separators A to E, may be replaced with a known type of cyclone or separator.

In summary, in the particle separator according to the present invention there is a space defined by the intermediate body or cylinder, the top wall of the upper body and the portion of the gas outlet pipe extending into the upper body. As a result, the incoming particle-laden gas will not be forced to form two vortices as would be the case in prior art devices, which results in a high pressure loss. The pressure loss across the particle separator in accordance with the present invention is about one third of that in the known type of cyclone type dust separators. However, the particle separator includes a conical lower body with a particle outlet so that the separation efficiency is substantially unimpaired.

Claims

1. Particle separating apparatus having a lower portion, an intermediate portion and an upper portion,in which the lower portion is in the form of a conical hopper having at its lower end an outlet for separated particles, the intermediate portion is substantially cylindrical and has a gas inlet pipe so positioned that, in use, the incoming particle laden ge- is caused to revolve or spiral within the intermediate body and the upper portion has a top wall spaced from the gas inlet through which a gas discharge pipe extends whereby, in use, the incoming gas spirals upwards and the particles are separated from it and collected.

2. Apparatus as claimed in Claim 1 including at least one upper trapping chamber communicating with the interior of the upper portion through a respective opening in the wall of the upper portion, whereby, in use, those particles which are carried upwardly with the gas pass into the trapping chamber and are collected.

3. Apparatus as claimed in Claim 2 including two substantially diametrically opposed upper trapping chambers extending substantially tangentially outwardly from the upper portion.

4. Apparatus as claimed in any one of Claims 1 to 3 in which the inlet pipe is spaced from the top wall by a distance of at least a quarter of the internal diameter of the intermediate portion.

5. Apparatus as claimed in any one of the preceding claims in which at least a portion of the wall of the upper portion is upwardly convergent.

6. Particle separating apparatus substantially as specifically herein described with reference to Figures 2, 3 and 4 of the accompanying drawings.

7. Material treatment apparatus including a furnace or kiln and a raw material particle preheater including at least one particle separating apparatus as claimed in any one of the preceding claims through which, in use, hot gas from the furnace or kiln flows and the raw material particles are preheated.

8. Cement calcination apparatus substantially as specifically herein described with reference to Figure 5 or 6 or 7 of the accompanying drawings including a particle separating apparatus as claimed in any one of Claims 1 to 6.